This invention relates to a waste water treatment apparatus for purifying soil water, such as waste water and sewage water discharged from agricultural facilities, by utilizing soil bacteria.
Techniques whereby waste water or the like from agricultural facilities is purified by the action of soil bacterial are known in the art. Japanese Patent Application No. 1993-10999B discloses the utilization of humus for cultivation and activation of such soil bacterial and the technique the humus is formed into pellets and these pellets are brought into contact with waste water under the aerobic condition in a water storage tank to obtain seed sludge. The equipment in which those pellets are packed is in some cases called a reactor by those skilled in the art. The reactor may be in other cases used to mean a combination of such a reactor and the water storage tank. However, the reactor, as used in the present invention, refers to the latter, i.e., the equipment in which those pellets are packed.
The above-described prior art employs one reactor for one water storage tank. The number of pellets packed in each water storage tank is increased in an approximate proportion to the treatment capacity of the water storage tank. For example, if the water storage tank has a waste water treatment capacity of 10,000 m3/day, approximately 1,200 kg of pellets are packed in the reactor. If the water storage tank has a waste water treatment capacity of 20,000 m3/day, approximately 2,400 kg of pellets are packed in the reactor. Notwithstanding the above, it has come within the knowledge of the inventors of this application that the amount of the pellets packed in an approximate proportion to the treating capacity of the water storage tank, if exceeds about 1,000 kg, retards a flow of the waste water and causes insufficiency of air supply in a central section of a pellet container to thereby hinder effective utilization of the pellets located in the central part of the pellet container. Also, the increased amount of the packed pellets leads inevitably to an increase in the size of the reactor. This requires the use of a large-sized machine in replenishing fresh pellets to or replacing the old pellets in the reactor, resulting in increasing cost for maintaining the waste water treatment apparatus.
It is accordingly an object of this invention to provide a waste water treatment apparatus which permits effective use of pellets that leads not only to the reduction in amount of the pellets needed for one water storage tank but also to the hold-down of the cost increase in maintaining the waste water treatment apparatus. The packing of the pellets, as described in the present invention, encompasses not only the case wherein the pellets are fully packed in the container or apparatus, but also the case wherein the pellets are packed in the container or apparatus to the extent that leaves a substantial volume of open spaces therein.
According to the present invention, there is provided a waste water treatment apparatus, which includes a water storage tank incorporated in a treatment process of organic waste water and a reactor disposed within the water storage tank. The apparatus is constructed such that the waste water in the water storage tank can be brought into contact with humus-containing pellets packed in the reactor under an aerobic condition so that soil bacteria is cultured in the waste water.
The water storage tank is provided with an inlet for receiving the waste water and an outlet where the waste water leaves the tank. A plurality of the reactors are disposed between the inlet and the outlet. Any of the reactors and containers attached to the reactors for packing the pellets therein is adapted to be removable from the water storage tank.